Appliances driven by electric motors are often required to operate at different rotational speeds. For example, when a drill driven by a motor is used for drilling holes, high speed operation is required, and when it is used for turning screws, low speed operation is required. Even though the motor may drive the appliance through a gearbox, sometimes the speed reduction provided by the gearbox is not sufficient or the use of a gearbox is not appropriate.
Speed and torque and battery voltage and current